Flood Maps Don't Consider Future Sea-Level Rise

NEW JERSEY - As people consider their rebuilding options in the wake of Sandy, it’s not clear if government agencies are providing the most up-to-date scientific information to states and municipalities regarding the likelihood of future flooding.

In particular, new coastal flooding maps from the Federal Emergency Management Agency (FEMA), while a great improvement over previous versions, do not integrate future sea-level rise, which is accelerating due to climate change.

Future sea-level rise will be significant for New Jerseyans. Ken Miller and Robert Kopp at Rutgers University project that local sea levels will rise about 1.3 feet by 2050 and about 3.1 feet by 2100 from their present-day levels. These are best-estimate projections and actual sea-level rise may be higher or lower. Because buildings and infrastructure along the coast are intended to last for decades, this information is crucial for sound long-term planning.

Please see detailed background information about the new maps and rising seas below. We hope you can integrate it into stories about rebuilding so people are aware that future sea-level rise poses additional risks to the state that are not fully accounted for in the new maps.

New flood maps from FEMA

New Jersey Governor Chris Christie announced on January 24th that the state would adopt new rules for building standards. Buildings will need to be reconstructed based on elevation recommendations embedded in new FEMA flood risk maps.

Although the new maps are in draft form, they provide crucial information for reconstruction and development decisions in communities struck by Sandy. The maps that have been released are an updated version of ones that have been in use since 1985. The new maps use the best available historical data to estimate flood risks, which have increased and are likely to affect more regions further inland.

In particular, the new maps integrate current estimates of historical sea level rise along the coast. But they do not yet take projections of future sea-level rise into account.

Future sea-level rise: the missing ingredient

In the past, FEMA has only been able to examine historical trends to estimate flood risk. But coastlines are dynamic and climate change is accelerating. The federal Flood Insurance Reform Act of 2012 may provide an opportunity for FEMA to integrate future projections of sea-level rise into its maps, assuming the law is implemented as intended and Congress provides adequate funding to the agency.

But for now, it’s important for New Jerseyans to understand the full measure of flooding risks they face.

Overall, sea-level rise is accelerating as heat-trapping carbon dioxide emissions from burning fossil fuels and destroying tropical forests accumulate in the atmosphere. As the Earth warms, the ocean expands and land-based ice melts into the ocean. One recent review of tidal data in Environmental Research Letters, found that the global rate of sea-level rise has tripled from the early 20th century.

The East Coast, in particular, is and will continue to be a hot spot for sea level rise. While the exact climate drivers of this rapid rise are not entirely known, local warming, ice melt, and circulation changes within the North Atlantic region may all be playing a role. At the same time, the region is slowly subsiding. Recent rates of sea level rise in points north of Cape Hatteras, North Carolina were 3 to 4 times higher than the global average, according to a recent study in the journal Nature Climate Change. Another study in Geophysical Research Letters found similar accelerating rates of sea level rise around Chesapeake Bay.

Are New Jersey communities using the best science?

When the governor’s office announced the new rules, they said the state was, “Using the best available science and data [to] give families, businesses, and communities the best assessment of their risk - allowing them to better mitigate damage from future flood events, avoid higher flood insurance costs, and begin the rebuilding process immediately.”

Unfortunately, amid all the other contentious issues rebuilding will bring up, there’s an important piece of science that is currently missing from the process.

It’s worth noting that New Jersey state law -- the Flood Hazard Area Control Act of 2007 -- mandates that buildings be elevated an extra foot above FEMA standards.

However, this safety buffer was not designed to account for sea-level rise. Additionally, rising seas have a magnifying effect on storm surges, which result from high winds pushing ocean water inland. And the effect of sea level rise on a specific area depends on the shape of the local coastline and ocean floor. In the future, FEMA’s sophisticated computer models could account for these projected changes.

More resources

Kenneth Miller is a professor in the Department of Earth and Planetary Sciences at Rutgers University. His faculty page includes links to his research and a slideshow presentation that captures how Sandy affected the Jersey Shore and projections and impacts of future sea-level rise on the region.

Robin Leichenko is a professor in the Department of Geography at Rutgers. She studies social and economic vulnerability to flooding and sea-level rise. Townships and municipalities vary greatly in how vulnerable they are to flooding and to events to like Sandy.

Rachel Cleetus, is an economist who specializes in climate change at the Union of Concerned Scientists (UCS). She has a blog post that explains how FEMA maps are used to inform rebuilding decisions and insurance rates and the role climate change could play in FEMA’s risk assessments. Generally, she writes, coastal communities can try to accommodate rising seas, retreat from them or adopt protective measures. But the riskiest path, she points out, is doing nothing. To make sound choices, communities need to be able to rely on the best available science, including projections of sea-level rise.

Celia Wexler, a member of UCS’s Center for Science and Democracy also has a blog post that covers the good, the bad and the ugly of integrating sea-level rise into state planning. Last year, she writes, the North Carolina legislature voted to bar state agencies from using accurate sea-level rise projections for coastal planning until 2016. In Virginia, the state legislature dropped references to climate change in favor of other terms after some lawmakers objected to recognizing climate science findings. By contrast, a regional Florida county compact and New York City are using peer-reviewed scientific assessments to inform planning decisions.